Bank account holders typically authenticate themselves at an ATM by inserting a card into a card slot (or by presenting some other identification token) and entering a personal identification number (PIN) on an encrypting keypad (implemented either as a physical keypad or as a screen rendered on a touch sensitive display).
Customers who have a visual impairment may not be able to use a touch sensitive display to enter their PIN because they cannot feel for a registration point (such as a raised bar on the “5” digit on a conventional encrypting PINpad). In addition, there is no tactile feedback from touching a touch sensitive surface. This makes using a touch sensitive display unreliable for those with some visual impairment, and almost impossible for those with no vision.
Furthermore, some bank customers are not numerate and have difficulty in remembering their PIN.
It would be desirable to provide an authentication mechanism that is as secure as conventional PIN, but that can be used reliably by those customers with visual impairments.